US2479072A - Electrical apparatus - Google Patents

Description

CROSS REFERENCE S R I SUBSTITUTE FUR MISSING XR ELECTRICAL APPARATUS 2 Sheets-Sheet 1 Filed Nov. 30, 1942 DIFFERENTIALLY HI 6 5 2555" 47 48 as .46 25 n F 17 g 26 3 3 a ll/ "41 J6 Q R38 I! i 7 E I 1 l I 50 41 l .59 23 16 52 5 go 37 46 Z8 5'H- I FIG. 5

Z8 FIG-1 54 {ll/ll/l/l/l/l/// 52 [11 m I r 1 I IIIIIRIIIIII 4-3 J] 17 I 152 42 Z3 .52 d MICROPHONE i8 7 21 a; 7

16' 1.9 Q1? Low- Jr c o I Wm FREQUENCY c J r O RECORDER a {P AMPLIFIER -INVENTOR i7 DETECTOR T OYAL LEE w HIGH-FREQUENCYL/ZO V B) OSCILLATOR METER ATTORNEY REARGR mm;

Aug. 16, 1949.

R. LEE

ELECTR I CAL APPARATUS Filed NOV. 30, 1942 FIG. 8 46 2 Sheets-Sheet 2 INVENTOR ROYAL LEE ATY'ORNEY Patented Aug. 16, 1949 UNITED STATES PATENT OFFICE 8 Claims.

microphone which is of simple and rugged construction and has a good response to impressed vibrations.

A still further object is to provide electrical apparatus which is so arranged as to form a simple and reliable dimension gauge.

The invention further consists in the several features hereinafter described and claimed.

In the accompanying drawings, illustrating certain embodiments of the invention,

Fig. 1 is a side elevation of a translating device incorporating features of the invention and arranged to form a microphone;

Fig. 2 is a sectional elevation taken generally along the line 2-2 of Fig. 1;

Fig. 3 is a sectional elevation taken generally along the line 33 of Fig. 2;

Fig. 4 is a sectional view taken generally along the line 4--4 of Fig. 3;

Fig. 5 is a detail sectional elevation taken generally along the line 5-5 of Fig. 3;

Fig. 6 is a detail view of a casing band of the device;

Fig. 7 is a diagrammatic view of an electrical system for the microphone;

Fig. 8 is an elevation of a modified form of microphone apparatus adapted for measuring or checking the surface finish of a work piece;

Fig. 9 is a front elevation of work-gauging apparatus arranged in accordance with the invention and adapted for gauging an opening in a work piece;

Fig. 10 is an enlarged sectional elevation of part of the work-gauging apparatus of Fig. 9;

Fig. 11 is a front elevation of a modified form of gauging apparatus adapted for gauging an external dimension of a work piece, and

Fig. 12 is a diagrammatic view of an electrical system for the gauging apparatus of Figs. 9 and 11.

Referring to Figs. 1 to '7 of the drawings, a microphone or signal translating device is designated generally by the numeral 15. The microphone includes coils l6 and i1 arranged in proximity to each other and relatively movable to vary the coupling between them. These coils, which form a variable inductor, are preferably connected in series and are arranged differentially or in opposing relation. The coils are of the spirally wound flat or pancake type arranged side by side in coaxial relation and are preferabl identical and of small size, usually considerably less than one inch in diameter. The coil spacing is small, being usually less than 1 inch.

The microphone coils are mounted for relative vibratory movement as hereinafter described, and are connected in a suitable electrical system such as that of Fig. 7. In this system, the variable inductor consisting of the two coils l6 and I! is connected across the input terminals of a detector or demodulator l8 and in some cases may be shunted by a small variable condenser IS. A high-frequency oscillator 20 of any suitable type, such as an electron-coupled type, impresses a high-frequency voltage on the input terminals of the detector. In some instances the oscillator may be crystal-controlled. The oscillator frequency is not critical and may be selected from a wide range of values such as from 30 kilocycles per second to 500 kilocycles per second, although these are not to be regarded as limiting values. In general, the use of the higher frequencies is desirable as the microphone coils can then be made small and light. The tuned parallel input circuit of the detector, comprising the connected microphone coils and their shunting capacities, is set to a frequency slightly above or below the oscillator frequency by adjusting the variable condenser [9 (or by adjusting the oscillator), so that the normal operating point of the detector is not at the crest of the resonance curve but lies on one of the sloping sides of the curve. The relative movement of the microphone coils under impressed mechanical vibrations changes the reactance of the detector input circuit, and thus produces a I correspondingly modulated detector output. The

The relatively movable microphone coils l6 and H are mounted within a metal shielding casin comprising a cylindrical cup 25 closed at its end by a disk 26. A hook-shaped bracket 21 within the casing is rigidly secured to the end wall of the cup by screws 28. Two parallel studs 29 are riveted to the bracket and extend in the diametral plane of the cup 25 and parallel to the axis of the cup. A flat plate 30 of insulating material extends at right angles to the cup axis and has apertured end portions slidably supported on the reduced threaded ends of the studs, the plate ends being confined between nuts 3| on the studs and compressed coiled springs 32 surrounding the studs. The flat microphone coil I6 is secured to the plate, as by a suitable adhesive, and is substantially coaxial of the casing. By turning the nuts 3 I, the plate and attached coil can be axially adjusted in the casing.

Two spring arms 33, preferably in the form of leaf springs, are spaced from opposite sides of the coil-supporting plate 30 and extend substantially parallel to the plate. The leaf springs, which have the shape seen in Fig.5, are each secured at one end to the bracket 2! as by screws 34, and each spring has its inner portions cut away to form a reentrant tongue 35 attached to the free end of the spring, thus increasin the effective length of the spring. A stem 35 of insulating material extends between the leaf springs along the axis of the casing and is rigidly secured at opposite ends to the aperture-d tongues 35 of the spaced springs, the stem extending through the apertured central portion of the coil-supporting plate 30. The end of the stem adjacent to the end wall of the cup 25 is fastened to the adjacent leaf spring by a nut 31, and the other end of the stem is fastened to the corresponding leaf spring by a screw threaded shank 38 formed on a fiat damp ing disk 39. The damping disk, which also forms on inertia member, fits loosely within the cylindrical cup 25 out of contact therewith A microphone cable 42, preferably of the coaxial type, is suitably anchored on the bracket 21, as by a terminal-forming grommet 43, and has its terminals connected to the coils I6 and H, the cable extending through an opening 44 in the casing cup 25. A pair of complementary cupshaped housing members 45 of insulating material snugly enclose the casing 25, 26 and have registering notches 46 at their meeting edges to accommodate the cable. The cup-shaped housing members have enlarged rim portions 41 which are retained in assembled relation by a surrounding resilient metal band 48 with inturned marginal flanges 49. The ends of the band are provided with complementary halves of a screw-threaded sleeve 50 through which the cable passes, and the split band is held in clamped position by a collar nut 5| surrounding the sleeve. The ends of the housing members are crowned and a loop member 52 is secured to one of these ends to receive a strap or tape, not shown, by which the microphone may be secured to a. vibration-transmitting surface. When the microphone is used for diagnostic work, in the manner of a stethoscope, the crowned end of the housing is placed against the body of a patient and the device is usually strapped or taped in position.

In operation, the vibrations of the source are transmitted to the contacting housing of the microphone, causing the housing and the parts of the device rigid therewith, including the coil IE, to vibrate in unison. The coil I'I, however, which is supported by the leaf springs 33, tends to remain stationary because of the inertia of the damping disk 33 and other parts rigid with the coil I7, and the result is a relative vibration of the two coils in accordance with the impressed vibrations. The inductance of the associated coils'IB and I1 varies accordingly, decreasing as the coils move toward each other and increasing as they move apart. The varyin inductance changes the reactance of the detector input circuit which is connected to the constant frequency oscillator 29, thus producing a modulated detector output. The resulting signal is then amplified and applied to one or more of the output devices 22, 23 and 24.

By connecting the microphone coils in series opposing relation, a relatively large change in inductance is effected for a comparatively small change in the coil spacing, thus improving the sensitivity of the device. The'normal spacing of the coils is not critical, although the spacing has an optimum value which is readily determined by experiment. The coil spacing is adjusted by turning the nuts 3|, the springs 32 serving to retain the adjustment. As the microphone may be used in various positions between vertical and horizontal, the normal coil spacing may vary slightly. However, by making the circuit adjustments with the microphone in about a 45 position, changes in the operating characteristics will be minimized. The normal coil spacing is not affected by the contact between the microphone and vibration-transmitting surface.

As the operation of the microphone depends on the relative position or coupling of the coils and not on the rate of change of coil displacement. the microphone is capable of responding to mechanical vibrations of relatively low frequency.

While the invention is here shown to be embodied in an inertia-type microphone, certain features of the invention are also applicable to microphones of the diaphragm type.

The modified form of microphone apparatus shown in Fig. 8 is adapted for measuring or checking the surface finish of a work piece. This apparatus includes a microphone or translating device I I5 which is generally similar to themicrophone I5 of Figs. 1 to 6 and is connected in a suitable electrical system such as that of Fig. 7.

In the modified microphone the coil I6 is sta-- 39 of Fig. 3 is omitted, and is replaced by a pin or stud I38 against which the inner end of the stylus abuts in coaxial relation to the coils, the microphone housing being centrally apertured to pass the stud. The stylus is here shown to, extend downwardly from the microphone housing, and passes through a centrally apertured flanged bushing I55 which is rigidly secured to the crowned end of the housing. The bushing is secured to a carriage I55 slidable on a guide member I57 in a direction at right angles to the stylus, the carriage being reciprocated as by means of a link I58. The plunger is urged downwardly by a light coiled spring I59 surrounding the plunger. A work holder I60, mounted on a support I6I below the microphone, is adapted to carry a work piece I62. In the case of a cylindrical work piece, such as a piston pin, the work holder may be in the form of a V-block.

In the operation of the device of Fig. 8, the tracing tip I54 of the stylus I53 is brought into contact with the work piece I62, and the microphone carriage is reciprocated, causing the stylus I53 to slide along the surface of the work piece. Any surface irregularities on the work piece will produce a vibration of the microphone coil I1,

and will be made evident by one or more of the output devices 22, 23 and 24 of the system of Fig. 7. The recorder 22 and voltmeter 24 may be calibrated to indicate the extent of the surface irregularities. The microphone is here shown to be movable with respect to the work but it will be evident that this relation may be reversed.

The modified form of apparatus shown in Figs. 9 and 10 is adapted for gauging or checking dimensions of a work piece. This apparatus includes a translating device 2I5 generally similar to the microphone of Fig. 8, although the device is not used as a microphone but rather as a displacement indicator. The translating device 2 I5 is secured in horizontal position to the underside of a bracket 263 mounted on a base 264. In this device the coil I1 is the movable coil and is arer is slidably mounted in a shouldered bore 268 formed in a cylindrical body member 269, the lower end of which is detachably secured in the ring member 265 by a set screw 210. The body member has a reduced cylindrical extension 21I at its upper end and is radially slotted to receive a bell-crank lever 212 which is pivotally mounted to swing about a horizontal axis. The lever 212 has a vertical arm which projects upwardly into the cylindrical extension 2H and is provided with a rounded contact portion 213 projecting laterally from the extension, the projection of the contact portion being limited by an adjusting screw 214 engageable with the horizontal arm of the lever and disposed in the upper end of the bore 268. The plunger is urged upwardly by a light coiled spring 215 but the adjusting screw 214 prevents the plunger from losing contact with the stud 238 on the coil-supporting stem of the translating device. The cylindrical extension 21I is adapted to receive'thereov'er an apertured work piece262 the inner diameter of which is to be gauged by theapparatus, this diameter determining the angular position of the bell-crank lever 212 and thereby determining the relative position of the coils I6 and I1 of the translating device.

The translating device 2I5 is connected in a suitable electrical system such as that shown in Fig. 12. In this system a high-frequency oscillator 220, similar to the oscillator of Fig. 7, is coupled to the input circuits of a bridge type vacuum tube voltmeter including a pair of vacuum tubes 216 and 211, preferably of the beam power type. The input or grid circuit of the tube 216 includes the variable inductor I6, I1, of the translating device, and in some instances a small adjustable shunting condenser 216, and the input or grid circuit of the tube 211 includes a coil. 219 and a small adjustable shunting condenser 288. The input circuits of the tubes are coupled to the oscillator by small condensers 28 I, and are tuned to a frequency slightly above or below the oscillator frequency, as in the system of Fig. 7. The vacuum or thermionic tubes have a common. cathode resistor 282, and the anodes or plates of the tubes are connected to a current source 283 through a center-tapped resistor 284, the ends of which are connected to the anodes. A directcurrent milliammeter 285, which may be of the zero-center or zero-end type, is connected between the tube anodes and is suitably calibrated. In the case of an instrument movement of the zero-end type, the normal current through the instrument is adjusted to bring the pointer to the,

center of the scale, as by adjusting the condenser 280'or the center-tapped resistor 284. same current source is used to supply the oscillator, a tuned choke 286 is connected between the source and the oscillator. The oscillator and associated apparatus, including the milliammeter 285, are housed in a suitable casing 281 mounted on the base 264.

In the operation of the apparatus of Figs. 9, 10 and 12, the work piece 262 is slipped over the vertical extension 21I of the body member, causing the bell-crank lever 212 to turn slightly on its pivotal axis and to depress the plunger 261 which in turn moves the coil I1 closer to the coil I6, thereby changing the inductance of the connected coils. The reactance of the input circuit of the vacuum tube 216 is thus changed, causing the plate current of this tubeto change and thereby altering the current flow through the milliammeter 285. The system of Fig. 12 is so adjusted that with a work piece having a bore of normal size the pointer of the milliammeter will be at the zero mark when the work piece is in gauging position. If the bore varies from normal size the meter pointer will come to rest at a position indicating oversize or undersize, as the case may be. By turning the work piece on the cylindrical extension 21I any eccentricities in the bore will cause changes in the pointer position.

The modified form of apparatus shown in Fig. 11 is adapted for gauging or checking the external dimension of a work piece, such as a cylindrical member 362, and is used in an electrical system such as that of Fig. 12. The apparatus includes a translating device generally similar to the devices of Figs. 8 and 9. The plunger or stylus of Fig. 8 is replaced by a plunger 353 which is urged in one direction by a coiled spring 359. The plunger is here shown to merely abut against the stud I36, but it will be obvious that the plunger may be rigidly attached to this stud in which event the spring 359 may be omitted. The mounting bushing I55 is secured to one leg of a U-shaped'frame 388, and the other leg of the frame is provided with an anvil member 399 in the form of a micrometer head screw-threaded in the frame and aligned with the plunger 353.

In the operation of the device of Fig. 11, which is connected in the electrical system of Fig. 12, the work piece 362 is inserted between the anvil 389 and the plunger 353, causing displacement of the coil I1 towards the coil I6. This efiects a deflection of the meter 285, as with the device of Fig. 9, thereby checking the diameter of the work piece. In some cases the inserted work piece may be turned to check any eccentricity.

Certain specific embodiments of the invention have been shown and described, but it will be un- If the adapted to transmit mechanical vibrations to one of said coils, means for resiliently mounting the other coil in said housing, and inertia means for resisting movement of said last-named coil during the vibration of the housing. 2. Electromechanical translating apparatus comprising electromagnetically coupled coils adapted to be traversed by high-frequency current and relatively displaceable to vary the coupling thereof, a vibratory support for said coils adapted to transmit mechanical vibrations to one of said coils, means for resiliently mounting another of said coils on said support, and inertia means for resisting the movement of said lastnamed coil during the vibration of the support. 3. Electromechanical translating apparatus comprising electromagnetically coupled coils adapted to be traversed by high-frequency current and relatively displaceable to vary the coupling thereof, a vibratory support for said coils adapted to transmit mechanical vibrations to one of said coils, means for resiliently mounting another of said coils on said support, and a damping member secured to said last-named coil and forming a damping chamber with said support.

4. Electromechanical translating apparatus comprising electromagnetically coupled coils adapted to be traversed by high-frequency current and relatively displaceable to vary the coupling thereof, a vibratory supporting housing for said coils adapted to transmit mechanical vibrations to one of said coils, means for resiliently mounting another of said coils in said housing, and an inertia plate secured to said last-named coil and forming a damping chamber with said housing.

- 5. Electromechanical translating. apparatus comprising electromagnetically coupled coils adapted to be traversed by high-frequency current and relatively displaceable to vary the coupling thereof, a vibratory enclosing support for said coils adapted to transmit mechanical vibrations to one of saidcoils, and a pair of spaced spring arms secured to said support for resiliently mounting another of said coils. 6. Electromechanical translating apparatus comprising 'electro magnetically coupled coils adapted to be traversed by high-frequency current and relatively displaceable to vary the coupling thereof, a support for mounting one of said coils, and a pair of spaced spring arms secured to said support and spaced axially of another of said coils for resiliently mounting said lastnamed coil.

7. Electromechanical translating apparatus comprising electromagnetically coupled coils adapted to be traversed by high-frequency current and relatively displaceable to vary the coupling thereof, a support, a pair of spaced spring arms secured to said support, said coils being disposed between said spring arms, means for mounting one of said coils on said support, and means including a member connecting the defiectable portions of said spring arms for mounting another of said coils.

8. Electromechanical translating apparatus comprising electromagnetically coupled coils adapted to be traversed by high-frequency current and relatively displaceable to vary the coupling thereof, a support having parallel studs, a carrier member for one of said coils slidable on said studs, coiled springs on said studs for urging said carrier member in one direction, screwthreaded members engaging said studs and forrning adjustable stops for the carrier member to vary the position of the associated coil, and resilient means for supporting the other coil.

ROYAL LEE.

REFERENCES CITED The following references are of record in the file of this patent: I

UNITED STATES PATENTS Number Name Date 281,240 Cheever July 17, 1883 314,155 Taylor Mar. 1'7, 1885 1,680,399 Thomas Aug. 14, 1928 2,005,887 Carson June 25, 1935 2,043,180 La Fave June 2, 1936 2,081,738 Conover May 25, 1937 2,083,759 Temple June 15, 1937 2,209,213 Vernon July 23, 1940 2,235,533 Roberts Mar. 18, 1941 2,261,541 De Sart Nov. 4, 1941 2,288,838 Pike et a1. July 7,1942 2,305,626 Lee Dec. 22, 1942 2,357,745 Kliever Sept. 5, 1944 2,364,237 Neif a Dec, 5, 1944 2,392,758. Minton Jan. 8, 1946 FOREIGN PATENTS Number Country Date 326,296 Great Britain Mar. 13, 1930 Patent No. 2,479,072

Certificate of Correction August 16, 1949 ROYAL LEE It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 2, line 26, for the numeral 500 read 5000; column 3, line 40, for the words forms on read forms an;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

' s Signed and sealed this 3rd day of January, A. D. 1950.

THOMAS F. MURPHY, Assistant Gammz'ssioner of Patents.

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